U-locks are commonly used for locking a bicycle to prevent theft of the bicycle. Ordinarily, a rider will lock the bicycle frame and at least one wheel to a post to secure the bicycle. Often, an experienced rider will remove the front wheel of the bicycle in order to lock it as well.
A U-lock principally includes a U-shaped bar with two substantially straight and parallel arms coupled to one another by a curved bow and a removable header. In the prior art the header has been a bar or tube which includes a passive hole and a locking hole each spaced about one inch from the opposite ends of the header. A rotating lock is fitted in the end of the header for securing the header to the U-shaped bar.
The U-shaped bar is made of metal bar stock formed into a U-shape with the arms of the bar in the range of four to six inches apart. A first arm includes a 90.degree. bend which is positioned about one inch from its end forming a short bar section. The second arm is formed to properly mate with the rotating lock of the header. Prior art U-locks are also designed to have two substantially straight parallel arms which are jointly locked within the header.
To lock the U-lock, the short bar section is placed into the passive hole and the U-bar and the header are rotated about the 90.degree. bend relative to one another so that the entire short bar section is pushed inside the header and the second end of the U-bar enters the locking hole. The rotating lock is then activated by a key to prevent the second end of the lock from being removed from the header thereby securely holding the lock closed. The straight arm U-locks are locked by inserting the locks into the header and activating the locking mechanism.
To lock a bicycle to a post or other object, the ends of the U-shaped bar are passed around the post and a portion of the frame and one tire (or both) of a bicycle. It is impossible to predict the thickness of the post to which a rider may desire to lock a bicycle. Further, bicycles are available with a variety of sizes of frame tubes, frame tube spacing, tires and wheels. U-locks are also used to lock motorcycles, boats, jet skis and many other objects.
It is possible and likely that the U-shaped bar of such a lock is longer than the combined dimension of the bicycle, tire and post. This excess length may be long enough to allow an unscrupulous person to insert an automobile jack or some other device between the arms of the U-shaped bar. Because an automobile jack is designed to lift the weight of an automobile, it is sufficiently strong to cause the U-lock to fail simply by forcing the lock open. A practiced thief can pre-size the jack to the proper spacing of the distance between the arms of the U-lock so that the jack need only be expanded to break the lock, allowing the thief to complete the theft in approximately twenty seconds.
To strengthen the U-lock and provide additional security, the prior art has used a security spacer which fits along the arms of the U-lock and blocks the space that can be left between the object being locked and the header. This type of security spacer is described in the U.S. patent application No. 07/755,546 by Richard H. Byrd filed on Sep. 5, 1991. This security spacer substantially fills the gap between the object being locked and the header to prevent the insertion of a jack and is held in place by the header.
While these security spacers do strengthen the U-lock and provide additional security, it is possible that there may still be enough space for an unscrupulous person to fit an automobile jack between the arms of the U-lock and cause it to fail. A U-lock in combination with one or more security spacers will withstand more pressure than a U-lock without a security spacer.
A bicycle thief will also fit the end of a pipe over the end of the header of the U-lock, putting pressure on the other end of the pipe in order to cause the lock to fail and the header to pop off. What is needed is a U-lock with a stronger, better designed header which will withstand greater pressure applied by an automobile jack and whose header end will not receive the end of a pipe.